Biology subjects

Drakesmith, H.

Publications and source records attributed to Drakesmith, H..

9 recordsLinked to original sources

bioRxiv2026

Regulation of Human Erythroferrone Expression

Erythroferrone (ERFE) is an erythroblast-secreted hormone that suppresses hepatic hepcidin expression to increase iron availability for erythropoiesis, ensuring recovery from anaemia. ERFE excess drives iron overload in disorders of ineffective erythropoiesis. Despite its pivotal role in systemic iron homeostasis and diseases of erythropoiesis, ERFEs molecular regulation has remained undefined. Here, we applied a genomic approach to characterise the molecular mechanisms governing ERFE expression. Using the HUDEP-2 human erythroid progenitor model, integrative ATAC-seq, CUT&RUN and micro capture-C analysis we identified a stage-specific accessible chromatin region within the ERFE 3 UTR that interacts with the promotor. We also identified enhancer-associated chromatin marks including H3K4me1 and H3K27ac in this region, and demonstrate that this cis-regulatory element is bound by key erythroid transcription factors KLF1, GATA1, TAL1 and STAT5. Functional dissection using CRISPR-Cas9-mediated deletion of the central 3 UTR enhancer element led to marked reduction in ERFE mRNA expression, and we show a corresponding reduction in nascent mRNA, confirming a key role for this region in transcriptional regulation. We define the transcriptional regulatory mechanism by which maturing human erythroblasts activate ERFE, the endocrine signal that coordinates erythropoietic demand with systemic iron mobilisation.

molecular biology↗

bioRxiv2025

Cell-type specific iron content regulation revealed by single-cell iron quantification

Iron is crucial for cellular metabolism and cell growth. Nevertheless, in humans, both iron deficiency and disorders of iron overload are widespread. How cellular iron content varies depending upon iron availability, and how this influences cell function is poorly characterised. We developed a method to quantify metals in hundreds of cells per minute via single-cell inductively-coupled plasma mass spectrometry (sc-ICP-MS), and used this to explore iron usage by immune cells. Activated murine T-cells exposed to a 625-fold titration of extracellular iron maintained close homeostatic control, with iron content varying by [~]20%. However, these variations strongly correlated with activation characteristics and proliferation. Running sc-ICP-MS downstream of flow cytometric sorting showed that murine T-cells and B-cells ex vivo exhibit similar mean and heterogeneity of cellular iron while splenic macrophages contain twice as much iron and more heterogeneous iron content. Finally, activated human B-cells contain [~]10-fold more iron per cell than murine B-cells. We suggest that mechanisms of iron homeostasis impart particular ranges or set-points of iron content to different cell types and activation states, and that small changes in iron content have large effects on cell behaviour. Our methodological advance and consequent findings suggest new approaches to studying the biology of metals.

cell biology↗

bioRxiv2024

Essential role of Hepcidin in host resistance to disseminated candidiasis

Candida albicans is a leading cause of life-threatening invasive infections with up to 40% mortality rates in hospitalized individuals despite antifungal therapy. Patients with chronic liver disease are at an increased risk of candidemia, but the mechanisms underlying this susceptibility are incompletely defined. One consequence of chronic liver disease is attenuated ability to produce hepcidin and maintain organismal control of iron homeostasis. To address the biology underlying this critical clinical problem, we demonstrate the mechanistic link between hepcidin insufficiency and candida infection using genetic and inducible hepcidin knockout mice. Hepcidin deficiency led to unrestrained fungal growth and increased transition to the invasive hypha morphology with exposed 1,3, {beta}-glucan that exacerbated kidney injury, independent of the fungal pore-forming toxin candidalysin in immunocompetent mice. Of translational relevance, the therapeutic administration of PR-73, a hepcidin mimetic, improved the outcomes of infection. Thus, we identify hepcidin deficiency as a novel host susceptibility factor against C. albicans and hepcidin mimetics as a potential intervention.

microbiology↗

bioRxiv2024

Aberrant iron deposition in the multiple sclerosis spinal cord relates to neurodegeneration

BackgroundIron accumulates in microglia-macrophages at the edge of multiple sclerosis (MS) lesions in the brain. Iron-rimmed brain lesions strongly predict disability accumulation, supporting iron metabolism is crucial in MS pathology. Little is known about iron distribution in the spinal cord. MethodsAutopsy cervical, thoracic and lumbar spinal cord samples from 9 controls and 46 MS donors of whom a subset (n=36) had mesiofrontal motor cortical tissue available for study, were labelled and systematically assessed for iron (DAB-enhanced Turnbull), myelin (PLP), axons (Palmgren silver), microglia-macrophages (TMEM119, Iba1, CD68), astroglia (GFAP), oligodendroglia (OLIG2), acute axonal injury (B-APP, SMI-32, NPY-1R) and oxidative stress (E06). MS lesional and non-lesional areas were considered. Total non-haem iron was quantified by inductively coupled plasma optical emission spectroscopy (ICP-OES). ResultsIn controls, iron predominantly localised to oligodendrocytes with total non-haem iron relating to total myelin fraction, which markedly differed in MS where iron accumulated in microglia-macrophages, subpial astrocytes, and axons in non-lesional areas. Iron laden microglia-macrophages were over-represented relative to total microglial-macrophages and displayed dysmorphic features. Iron-positive axons showed a disto-proximal gradient (highest at lumbar level) with a predilection for the corticospinal tracts. The extent of iron axon positivity related to smaller spinal cord area, lower total axonal counts, and greater oxidative stress. Iron positivity in each cellular compartment (i.e. subpial astrocytes, microglia-macrophage and axons) related to one-another and total non-haem iron correlated with axonal counts in MS. No iron-rimmed lesions were detected in the spinal cord unlike in cortical grey and subcortical white matter of the same cases where 22% and 80% of iron-rimmed lesions, respectively, were seen. ConclusionsDespite the conspicuous absence of iron-rimmed lesions in the MS spinal cord, we demonstrate widespread aberrant iron distribution in the MS spinal cord that relates to oxidative stress and neurodegeneration independent of demyelination. The distal cord predominant and corticospinal tract specific accumulation of iron in axons mirrors the pattern of length-dependent motoric disability commonly encountered in progressive MS. These findings implicate aberrant iron accumulation as a novel, clinically relevant, feature of MS spinal cord pathology.

neuroscience↗

bioRxiv2024

Iron deficiency causes aspartate-sensitive metabolic and proliferative dysfunction in CD8+ T cells

Iron is an irreplaceable co-factor for metabolism. Iron deficiency affects >1 billion people, causing symptoms including anaemia and impaired immunity. Nevertheless, precisely how iron deprivation impacts immune cell function remains poorly characterised. We therefore interrogated how physiologically low iron availability affected activated CD8+ T cell metabolism and function, using multi-omic and metabolic labelling approaches. Iron limitation profoundly stalled proliferation without influencing cell viability, altered histone methylation status and disrupted mitochondrial membrane potential. Consistently, metabolism of glucose and glutamine in the TCA cycle was limited, indeed TCA cycle activity was partially reversed to a reductive trajectory. Previous studies have shown mitochondria-derived aspartate is crucial for proliferation of transformed cells. Surprisingly, we found aspartate was increased in stalled iron deficient CD8+ T-cells, but was not utilised cytosolically for nucleotide synthesis, likely due to trapping within depolarised mitochondria. Conversely, exogenous aspartate, which directly accesses the cytosol, markedly rescued the clonal expansion of even severely iron-deficient CD8+ T-cells. Overall, iron scarcity creates a mitochondrial-located metabolic bottleneck impairing T-cells, which can be bypassed by resupplying inhibited biochemical processes with aspartate. These findings reveal molecular consequences of iron deficiency for CD8+ T cell function, providing mechanistic insight into the basis for immune impairment during iron deficiency.

immunology↗

bioRxiv2023

Novel role of bone morphogenetic protein 9 (BMP9) in innate host responses to HCMV infection

Herpesviruses modulate immune control to secure lifelong infection. The diverse mechanisms Human Cytomegalovirus (HCMV) employs in this regard can reveal unanticipated aspects of cellular signalling involved in antiviral immunity. Here, we describe a novel relationship between the transforming growth factor-beta (TGF-{beta}) family cytokine bone morphogenetic protein 9 (BMP9) and HCMV infection. We identified cross-talk between BMP9-induced and type I interferon (IFN) receptor-mediated signaling, showing that BMP9 boosts the transcriptional response to and antiviral activity of IFN{beta}, and thereby enhances restriction of HCMV replication. We also show that BMP9 is secreted by human fibroblasts upon HCMV infection. However, HCMV infection impairs BMP9-induced enhancement of the response to IFN{beta}, indicating that this innate immune signalling role of BMP9 is actively targeted by HCMV. Indeed, we show that transmembrane proteins US18 and US20, which downregulate type I BMP receptors, are necessary and sufficient to cause inhibition of BMP9-mediated boosting of the antiviral response to IFN{beta}, so that HCMV lacking US18 and US20 is more sensitive to IFN{beta}. These results demonstrate that HCMV has a mutually antagonistic relationship with BMP9 and substantially extend the growing body of evidence that BMP signalling is an underappreciated modulator of innate immunity to viral infection.

immunology↗

bioRxiv2023

Cellular iron governs the host response to malaria

Malaria and iron deficiency are major global health problems with extensive epidemiological overlap. Iron deficiency-induced anaemia can protect the host from malaria by limiting parasite growth. On the other hand, iron deficiency can significantly disrupt immune cell function. However, the impact of host cell iron scarcity beyond anaemia remains elusive in malaria. To address this, we employed a transgenic mouse model carrying a mutation in the transferrin receptor (TfrcY20H/Y20H), which limits the ability of cells to internalise iron from plasma. At homeostasis TfrcY20H/Y20H mice appear healthy and are not anaemic. However, TfrcY20H/Y20H mice infected with Plasmodium chabaudi chabaudi AS showed significantly higher peak parasitaemia and body weight loss. We found that TfrcY20H/Y20H mice displayed a similar trajectory of malaria-induced anaemia as wild-type mice, and elevated circulating iron did not increase peak parasitaemia. Instead, P. chabaudi infected TfrcY20H/Y20H mice had an impaired innate and adaptive immune response, marked by decreased cell proliferation and cytokine production. Moreover, we demonstrated that these immune cell impairments were cell-intrinsic, as ex vivo iron supplementation fully recovered CD4 T cell and B cell function. Despite the inhibited immune response and increased parasitaemia, TfrcY20H/Y20H mice displayed mitigated liver damage, characterised by decreased parasite sequestration in the liver and an attenuated hepatic immune response. Together, these results show that host cell iron scarcity inhibits the immune response but prevents excessive hepatic tissue damage during malaria infection. These divergent effects shed light on the role of iron in the complex balance between protection and pathology in malaria.

immunology↗

bioRxiv2022

Plasma iron controls neutrophil production and function

Low plasma iron (hypoferremia) induced by hepcidin is a conserved inflammatory response that protects against infections but inhibits erythropoiesis. How hypoferremia influences leukocytogenesis is unclear. Using proteomic data, we predicted that neutrophil production would be profoundly more iron-demanding than generation of other white blood cell types. Accordingly in mice, hepcidin-mediated hypoferremia substantially reduced numbers of granulocytes but not monocytes, lymphocytes or dendritic cells. Neutrophil rebound after anti-GR1-induced neutropenia was blunted during hypoferremia, but was rescued by supplemental iron. Similarly, hypoferremia markedly inhibited pharmacologically-stimulated granulopoiesis mediated by GCSF and inflammation-induced accumulation of neutrophils in the spleen and peritoneal cavity. Furthermore, hypoferremia specifically altered neutrophil effector functions, suppressing antibacterial mechanisms but enhancing mitochondrial ROS-dependent NETosis associated with chronic inflammation. Notably, antagonising endogenous hepcidin during acute inflammation enhanced production of neutrophils. We propose plasma iron modulates the profile of innate immunity by controlling monocyte-to-neutrophil ratio and neutrophil activity in a therapeutically targetable system.

immunology↗

bioRxiv2020

cGAMP loading enhances the immunogenicity of VLP vaccines

Cyclic GMP-AMP (cGAMP) is an immunostimulatory second messenger produced by cGAS that activates STING. Soluble cGAMP acts as an adjuvant when administered with antigens. cGAMP is also incorporated into enveloped virus particles during budding. We hypothesised that inclusion of the adjuvant cGAMP within viral vaccine vectors would promote adaptive immunity against vector antigens. We immunised mice with virus-like particles (VLPs) containing the HIV-1 Gag protein and VSV-G. Inclusion of cGAMP within these VLPs augmented splenic VLP-specific CD4 and CD8 T cell responses. It also increased VLP- and VSV-G-specific serum antibody titres and enhanced in vitro virus neutralisation. The superior antibody response was accompanied by increased numbers of T follicular helper cells in draining lymph nodes. Vaccination with cGAMP-loaded VLPs containing haemagglutinin induced high titres of influenza A virus neutralising antibodies and conferred protection following subsequent influenza A virus challenge. Together, these results show that incorporating cGAMP into VLPs enhances their immunogenicity, making cGAMP-VLPs an attractive platform for novel vaccination strategies. Short summarycGAMP is an innate immune signalling molecule that can be transmitted between cells by inclusion in enveloped virions. This study demonstrates enhanced immunogenicity of HIV-derived virus-like particles containing cGAMP. Viral vectors loaded with cGAMP may thus be potent vaccines.

immunology↗